/Engine/Source/Runtime/InteractiveToolsFramework/Public/InputState.h
Current State of a physical device button (mouse, key, etc) at a point in time. Each "click" of a button should involve at minimum two separate state events, one where bPressed=true and one where bReleased=true. Each of these states should occur only once. In addition there may be additional frames where the button is held down and bDown=true and bPressed=false.
struct FDeviceButtonState
bool
bDown
Is the button currently pressed down. This should be true every frame the button is pressed.
bool
bPressed
Was the button pressed down this frame. This should happen once per "click"
bool
bReleased
Was the button released this frame. This should happen once per "click"
FKey
Button
Button identifier